LONDON (Reuters) - Dogs are probably much cleverer than most peoplethink, according to a new study.

Scientists are convinced that dogs can count and researchers at theUniversity of California Davis say they try to convey different messagesthrough the pitch and pace of their barks.

"Animal behaviorists used to think their bark was simply a way of gettingattention. Now a new study suggests that individual dogs have specificbarks with a range of meanings," New Scientist magazine said onWednesday.

Dogs usually use high-pitched single barks when they are separated fromtheir owners and a lower, harsher super bark when strangers approach orthe doorbell rings, according to Sophia Yin, an animal behaviorist at theuniversity.

Playful woofs are high-pitched and unevenly spaced.

Dogs also know when they are being short-changed on treats because they
have a basic mathematical ability which enables them to tell when one
pile of objects is bigger than another.

"But to count, an animal has to recognize that each object in a set
corresponds to a single number and that the last number in a sequence
represents the total number of objects," New Scientist added.

Robert Young of Brazil's Pontifical Catholic University of Minas Gerais
in Belo Horizonte, tested the theory on 11 mongrels using dog treats.

The canines were shown treats and then a screen was lowered and the
goodies were left as they were or some were added or taken away.

If a treat was added or taken away the dogs looked at the treats much
longer than they did when the goodies were not disturbed, presumably
because they had done their sums and the numbers did not meet their
expectations.

"Dogs are descended from wolves, which not only have a large neocortex --
the brain's center of reasoning -- but live in large social groups," the
magazine said.

Young believes the mathematical ability could have been used to work out
how many allies and enemies they had in a pack.